1. Field of the Invention
The invention relates, in general, to gas and other material for testing devices and, in particular, to a new and useful test tube with an indicator for the colorimetric indication of substances to be detected which has an opening that is closed against the environment with a hydrophobic membrane permeable to the substances to be detected.
A similar test tube has become known from Canadian Patent No. 1,157,355.
The known test tube has an opening that is closed with a permeable membrane through which harmful gaseous substances reach from the atmosphere to an indicator and there lead to coloration. By selecting suitable membrane materials, for example silicon rubber, a deliberate selectivity for the harmful gaseous substance to be detected is achieved.
The known test tube is used for demonstrating the presence of gaseous harmful substances in the ambient air. The increasing pollution of water with water-soluble harmful substances, however, also requires that water be monitored. For measuring chemical pollution in samples of water, according to DE-Z, Dragerheft 325, pages 18 to 20 (1983), an appropriate suitable test tube is connected to a washing bottle in which is contained the test sample of water. With a connected gas detector pump, air is pumped through the washing bottle which absorbs the harmful substance to be detected and carries it through the test tube. Carrying out such measuring method is cumbersome and requires several pieces of apparatus adjusted to each other such as washing bottle, test tube, and transporting pump.